1. Field of the Invention
This invention relates to a radio antenna. With the miniaturisation of electronic equipment for telecommunications it has become desirable to develop correspondingly small yet efficient radio antennas. This has been achieved by using reactive tuned forms of conventional wire antennas, but these have restricted bandwidths and reduced efficiency. It is the object of this invention to provide an antenna system which has improved operational efficiency and which has wideband characteristics.
2. Description of the Prior Art
This invention uses the Poynting Vector Synthesis, such as disclosed in GB 2 215 524 and U.S. Pat. No. 5,155,495, in which the antennas create radiation from out of phase voltages applied to a conductor plate and either a coil, or a second plate. Electric and magnetic fields are made to cross each other at right angles with a precise amount of out-of-phase in the cycle. In the present invention the same principles are used, but instead of two out-of-phase voltages being applied to plates, out-of-phase currents are used in closely spaced wire conductors.
It is the presently accepted view that a radio wave may be imagined theoretically as consisting of a pair of transverse alternating fields, one electrical and one magnetic, travelling in phase at the velocity of light, geometrically orthogonal and absolutely synchronous. When examined at a great distance from their source the said fields are an almost perfect plane wave as shown in the drawings illustrating two partial representations:
FIG. 1 shows the plane wave as a Poynting Vector. E is the radio frequency electric field, units Volts per metre; H is the radio frequency magnetic field, units Amp-turns per metre; S is the vector representing outward power-flow density and is in units of Watts per square metre. Mathematically S is the vector cross product of the electric field with the magnetic field, written in terminology of vector maths: S=E.times.H. Exactly half the power is in each field, and their magnitude relationship being set by the natural space impedance Zo given by: Zo=.vertline.E.vertline./.vertline.H.vertline.
FIG. 2 shows the waveform phase relationships of the components of the Poynting Vector for the plane wave as a time function.